Grommet



Aug. 15, 1950 w. n ANDERSON GROIIET Filed lay 22. 1945 Patented Aug. 15,1950 UNITED STATES PATENT OFFICE Warren K. Anderson, Pacific Palisades,Calm, assigner to Douglas Aircraft Company, Inc.,

Santa Monica, Calif.

Application May 22, 1945, Serial No. 595,159

4 Claims. I 1

This'invention relatesto grommets, particularly those adapted to beinserted in an aperture formed in a bulkhead or the like for passing aconduit therethrough. The purpose of this type of grommet is to protectsuch conduits as are susceptible to abrasion or wear, from frictionalcontact with the sharp or relatively thin edge of the aperture.

Grommets heretofore proposed for this purpose comprise a ring split onone side of its axis of revolution by. a plane of cleavage extendingdirectly towards the center of the ring along a radius 01 the ring. Whenthe grommet is contracted radially to insert it into the aperture or toremove it therefrom, the ends of the split grommet invariably overlapcircumferentially and bind. radially against each other, preventingdirect radial expansion of the ring. To expend such a grommet into itsaperture thus necessitates the application of pressure to the adjacentends of the grommet in opposite directions circumferentially of thegrommet; that is, the ringhas to be pulledsomewhat apart. Thischaracteristic of such grommets renders the seating or application ofthe grommet comparatively diflicult and rather time wasting for anoperation of relatively minor importance.

The present invention provides a grommet which can be quite easilyinserted in an aperture in a bulkhead or the like and which looks itselfin place therein without requiring any of the aforementionedcircumferential stretching section of the cleavage plane with theperiphery of the ring. An end of the ring can hence be a compressedinwardly of the ring, along a spiral path, while the other end isanchored against the periphery of the aperture. The ring in thiscontracted condition can then be inserted coaxially in the aperture withits periphery in engagement with the periphery of the aperture.

Upon substantial completion of the peripheral interengagement, the otherend of the ring then snaps into abutment with the anchored end, movingoutwardly in a spiral, or non-radial direction to do so. The expansivetendency of the ring securely holds the so disposed ring in placeagainst the periphery of the aperture. In order to further secure thegrommet in place against displacement by unusually violent forces, itsperiphery may be provided with means, such as an annular groove, forpositively interengaging with the periphery of the aperture.

To remove the grommet, it is only necessary to compres one end inwardly,away from engagement with the periphery of the aperture, the end movingalong a spiral pathway, the fingers at the same time urging the endslightly outwardly of the plane of the ring. The remainder of the ringthen easily disengages itself from the periphery of the aperture, due tothe inward contraction transmitted around the periphery, coupled withthe outward pull on the free end of the ring.

The surfaces of the ends of the ring are rendered planar and parallelwith reference to each other by the dual inclination of the plane ofcleavage, so that, either in installing or removing 'the grommet, thesesurfaces move in parallelism along their non-radial paths. Since thefree end of the ring, in contracting or expending it, moves along a lineextending at an e tie to the diameter of the ring passing through 1/intersection of the cleavage plane with the iphery, at no position inits movement does it lverlap or lie directly or radially behind theother end of the ring. It is thu impossible for these ends to assume aposition in which one end can bind radially against the other. Hence, itis unnecessary to circumferentially separate the ends, or pull the ringapart, as in the prior types of split grommets, in order to fit thegrommet into place in the aperture.

Preferably, the grommet is formed of some comparatively stifi andshape-retaining material, and it is also desirable. that this materialbe of such a composition as to have a certain amount of resiliencydespite its shape-retaining nature. This resiliency enables the ring tobe more easily fitted into position in the aperture 01' to be removedtherefrom, and facilitates its also has suiiicient resiliency to permitthe memher It to be contracted or expanded and to yield The otherconcepts and accomplishments of the invention will become manifest asthis spec'i-'- flcation proceeds.

One of the presently preferred embodiments of the inventivejconcepts isillustrated, by way of example only, in the accompanying drawings anddescribed hereinafter with reference to said drawings. It is to beunderstood, however, that the invention is limited in the embodimentswhich it can take only by the scope of the accompanying claims.

In these drawings,

Figure l is a perspective view of the grommet;

Figure 2 is a side View of the grommet mounted in a bulkhead, showingthe latter in section; and

Figure 3 is a plan view of the grommet showing the same partiallyinstalled in an aperture in a bulkhead.

Referring now more in detail to the drawings,

slightly under axially opposite pressures, thereby permitting the ringto be contracted for insertion into and removal from the aperture. Italso permits the ends II and I! to be abutted to expand the ring andeffect a self-locking action of the ring in the aperture.

Due to the non-radial direction of the plane of cleavage, when an end ofthe ring is inwardly compressed, preparatory to inserting the grommet inthe aperture, its planar face will move inthe grommet of the presentinvention comprises surfaces l3 and [4 on these ends which, whenextended inwardly of the ring, intersect the axis of revolution of thering at a point lying outside the ring. The point of intersection alsolies either below'or above the major plane of the ring, depending uponwhether the plane of cleavage slants to the right, as in the drawings,or to the left. The plane of cleavage is also angularly displaced withreference to a diametral line passing through the point of intersectionof the cleavageplane with the periphery. The cleavage plane henceintersects the upper and lower faces of the ring along non-radial linesI! and I5, and, due to its inclination with respect to the axis ofrevolution, intersects the inner and outer faces of the ring alongdiagonallines l6 and I1.

Preferably, but not necessarily, each of the aforementioned angles ofinclination is of the order of 45 with reference to the respective datumlines mentioned, as it has been found that the employment of thisparticular angle facilitates the mounting and removal of the ring.

It is not absolutely essential that the plane of cleavage be inclinedwith reference to the axis of revolution, however, so long as it isangularly displaced with reference to the diametral line passing throughthe point of intersection of the cleavage plane with the periphery ofthe ring.

Dueto this construction of the ring, one end thereof may be anchored orheld in engagement with the wall of an aperture and prevented frommoving, while the opposite end is contracted in a roughly spiral path toa position inwardly of the anchored end. This feature of constructiongreatly facilitates the mounting or removal of the grommet with respectto the aperture it is to fair, as will be made manifest hereinafter.

The member ill is provided with a medial peripheral groove [8 whichreceives the edge of the circular aperture when the ring is snapped intoplace therein. In order to facilitate this snap action, the member I0 ispreferably constituted of a plastic which, although relatively still andshape-retaining in its nature, nonetheless wardly along a non-radialline. This line extends in substantial continuation of the plane ofcleavage, and lies at an angle to the diameter of the ring at that pointof its periphery that is intersected by the plane of cleavage. The lineusually constitutes a portion of a spiral or a secant that is less thana diameter. Consequently, either when contracting or expanding thegrommet, the planar faces I! and I remain in parallelism, so that theycan always slide inwardly and outwardly, in contact with each otherwithout overlapping. Therefore, one end of the ring cannot assume aradially offset position with respect to the other. Hence. no radialengagement or interference of radially squared-off ends, as in the priorgrommets, and set up by circumferential overlap, can occur. 1

In mounting the grommet, as in an aperture in a bu khead, one endportion thereof is pressed spirally inwardly of the ring, the extremityof this portion being constrained to move along a line extending at anangle to the diameter of the ring that meets the periphery where theplane of cleavage also intersects the periphery. The ring, in thiscondition, is then inserted coaxlally in the aperture with the peripheryof the inwardly compressed end portion in engagement with one portion ofthe periphery of the aperture. The remainder of the periphery of thering is then fitted into engagement wi h the rest of the periphery ofthe aperture until the unanchored end of the ring is in juxtapositionwith the first end, whereupon the unanchored end snaps into abutmentwith the anchored end, moving spirally outwardly on a non-radial lineinto engagement with the periphery of the aperture. Usually, but notnecessarily, the parallel faces of these ends move in contact with eachother, the sliding being facilitated by the low coefficient of frictionof the material as well as by the dual inclination of each face. Theresilient grommet is thus easily fitted into place with its peripheryfirmly engaging all around the periphery of the aperture, and itstendency to expand secures it against the periphery of the aperture.

In order to remove the grommet, one end is compressed inwardly, movingalong a spiral path, and being at the same time urged by hand slightlyout of the plane of the bulkhead. The remainder of the periphery of thering then easily disengages itself from engagement with the periphery ofthe aperture, this disengagement being facilitated, if desired, bypulling outwardly on the free end while maintaining the inwardcompression thereof.

When the grommet is full positioned in the aperture in the bulkhead,with the edge of the aperture fully entering the groove l8 all aroundthe periphery of the grommet, the outwardlyiacting inherent springaction or resiliency of the ring "I, due to its shape andcomposition,will cause the grommet to tightly maintain itself in auaaoi ment of thering by axially directed forces.

It is to be understood that the grommet is to be. inserted or removedfrom its self-locking engagement in the aperture, solely by the use ofthe fingers applied thereto as aforedescribed, no tool of any naturewhatever being required to insert or remove the grommet. The shape andnature of the surface of the grommet are such as-to set up little or nofriction between the grommet and a rubber-covered, or other wire, orconduit, passing through the same. Due to the toroidal shape and to thelow coeflicient of friction of the material, the movement of a movablecable through the aperture is facilitated to a substantial degree,without danger of abrasion, by the presence of the grommet as comparedto the movement of a movable cable through an aperture not provided withthe grommet. Although thegrommet is relatively easy to seat inengagement with the edge defining the aperture, and equally as easy toremove from its seated engagement and from the aperture, theself-locking feature, coupled with the resiliency and shape of the ring,provide secure and permanent anchorage of the ring in the desiredposition until directed forces are positively applied and the ring ispositively and deliberately manipulated with an intent to remove it.There is little danger, therefore, of accidental displacement of thering from the aperture so that conduits can be moved back and forth withconsiderable violence in contact with the grommet withoutliability oftheir eventually working the gromm'et out and becoming abraded anddisintegrated by the sharp edge 'of the aperture.

The grommets of this invention are well adapted for manufacture on thelarge-quantity scale; A material of a composition capable of conferringa' shape-retaining, but resilient character upon the grommet, such asone of the thermo-plastics in the plastic phase, may be molded orstamped into a plurality of the articles. Or, if desired, an extrusionof this material may be formed into a continuous helix having anydesired cross-sectional shape. While still somewhat plastic, each of theconvolutions of the helix, at corresponding points along,the length ofthe helix, is severed with a suitably constructed gangshear or the like.a

The blades of this shear are set at such an angle with reference to theconvolutions of the helix as to simultaneously divide all theconvolutions along a plane of cleavage that is angularly displaced, ineach convolution, with reference to that diametral line of theconvolution that intersects the periphery of the convolution. The helixis thus simultaneously separated into a plurality of split, toroidalbodies, each having abutting ends with planar faces, each of these faceslying in a plane angularly oilset, as above described, with reference tothe aforementioned diameter and axis of revolution.

Various refinements and ramifications of the particular structural partsand shapes illustrated in the drawings are contemplated by theinvention, and all lie within the scope of the subjoined claims. I

I claim: I

1. A grommet constructed to be axially inserted in and removed from anaperture in a partition which is laterally inaccessible and axiallyaccessible from the one face only, comprising: a

ring divided along a plane of cleavage at one side of the axis ofrevolution, the plane of cleavage being inclined to the axis ofrevolution and being displaced at an acute angle from the diametral lineextending from said axis to the point of the periphery where the planeof cleavage intersects the periphery, said ring being composed of com'-'paratively stiff, shape-retaining material having sufficient resiliencyto permit the ends of the ring to be expanded and contracted towards andaway from said axis, said ring having an outer peripheral groove, one ofthe portions of the ring adja ent the plane of cleavage being movablealong a spiral path to enable the ring to be axially inserted into anapertureand thereafter to radially expand into interengagement with theperiphery of the aperture whereby the grommet may be engaged with theperiphery of said aperture with the fingers of one hand andindependently 'of applicator tools without overlapping, jamming orbinding of said ends.

2. A grommet constructed for axial insertion and radial expansion intoan aperture in a planar partition, comprising: a generally circular,discontinuous, ring of comparatively stifi, shaperetaining materialhaving sumcient resiliency to permit the ends of the ring to becontracted and expanded toward'and away from the axis of revolutionthereof; said ring having an outer peripheral groove for interengagementwith the wall of said aperture; the ends of said ring having subalong aplane of cleavage which intersects theaxis of revolution of said ringat'a point lying outside of the major plane of said ring; whereby saidends may be serially moved into mounted position in said aperturewithout mutual interference to provide a minimum gap in said ring whenfully expanded into position.

3. A grommet constructed for axial insertion and radial expansion intoan apertureina planar partition, comprising: a generally circular ringdivided at one point in its circumference to provide a pair of endshaving substantially planar faces confronting each other along a planeof cleavage; said ring being formed of comparatively stiff,shape-retaining material having sufiicient resiliency to permit the endsto be contracted' and expanded toward and away from the axis ofrevolution of said ring, and having an outer peripheral surface formedfor interengagement with the wall of said aperture; said plane ofcleavage being displaced at an acute angle from the diametral lineextending from the axis of revolution to the point of the circumferencewhere the plane of cleavage intersects the circumference; whereby afirst end, the intermediate portion, and a second end of said ring maybe serially moved into mounted position in said aperture without mutualinterference, with said second end in its final stage movingsubstantialv and radial expansion into an aperture in a planarpartition, comprising: a generally circular ly stiff, shape-retainingmaterial having sumcient resiliency to permit the ends to be contractedand expanded toward and away from the axis 1 of revolution of said ring,and having an outer peripheral surface formed for interengagement withthe .wall of said aperture; said plane 0'! cleavage being displaced atan acute angle from the diametral line extending from the axis ofrevolution to the point of the circumi'erence where the plane ofcleavage intersects the circumterence, and intersecting said axis oi.revolution at a point lying outside of the major plane of said-ring;whereby a first end, the intermediate portion, and a second end 01' saidring may be serially moved into mounted position in said aperturewithout mutual interference to provide a minimum gap in said ring whenfully expanded into position.

WARREN K. ANDERSON.

REFERENCES CITED UNITED sums PA'I'ENTS Number Name Date 205,165 WoodruflJune 18,1878 664,143 Garlock Dec, 18, 1900 898,786 Saunders Sept. 15,1908 10 1,084,281 King Jan. 13, 1914 1,415,632 Gurke May 9, 19221,697,814 Forbes Jan. 1, 1929 1,873,859 Bailey Aug. 23, 1932 2,355,126Webster et a1 Aug. 8. 1944 Brown Jan. 23, 1945

